Process and press for manufacturing glued blocks

ABSTRACT

The invention relates to a process and a device for the manufacturing of a glued block made of triangular cross-sectioned elongated staves of wood. The staves of wood are laid beside each other with alternate staves with their base sides downwards and alternate ones with their base sides upwards, and adhesive applied between adjoining surfaces between the staves. A press ( 13, 14, 21-33 ) applies main pressure force to glue the staves firmly together is transverse to the base sides of the staves.

The present invention relates to a process for manufacturing gluedblocks, and a device for performing the process.

BACKGROUND OF THE INVENTION

In order to get as much as possible shape-stable wood material with ahard surface and a pleasing appearance out of a log of wood, a so-calledstar-sawing technique is used in certain cases which gives, amongstothers, triangular staves of wood. One such technique is described, forexample, in the Swedish patent application No. 9100830-0. Thesetriangular staves of wood can then be laid beside each other with theirbases alternately turned upwards and downwards and joined together toform a large block. This block can be used as it is for table tops,floor material or the like but it can also be sawn up into thinnerand/or narrower boards along or across the direction of the grain.

During manufacturing of glued blocks where the material consists oftriangular starsawn wooden elements there sometimes occur large problemsin getting the block perfectly glued when conventional techniques areused. The problems consist, amongst others, in that the friction forceson the upper and lower surfaces are much greater in the case where theforce is applied in the conventional manner against the longside edges,i.e. against the outermost staves of wood in a laid-out series of stavesof wood. The pressure from the press is lost the closer one gets to themiddle of the block, which means that the glued joints near the middlebecome less durable.

WO 83/03791 describes a method and arrangement for making glue jointblocks according to the priorly known technics (see especially pages 11and 12). The triangular staves of wood are provided on place between thelateral pressure plates which then are place having a distance betweenthem adapted to the pattern of triangular staves which are layed on alower board. In order to keep the staves on place during the pressureprocedure the staves having their bases upwards are pressed down alittle such that their tops are protruding downwards between the basesor the staves having their bases downwards and then fixed in thatposition. After that the pressure proceeding begins by pressing thelateral pressure plates together. Thus the pressure is here providedagainst the outer staves in the block.

OBJECTS OF THE INVENTION

One object of the process and device according to the invention is toachieve durable glue joints between essentially triangular staves ofwood which are laid beside each other.

Another object of the process and device according to the invention isto achieve a glue joint between staves of wood laid beside each otherwhich is satisfactory all the way through to the surface of the blockformed from them.

These objects are attained with a process according to claim 1. Furtherfeatures and developments, and a device for performing the process, arementioned in the other claims.

BRIEF DESCRIPTION OF THE FIGURES

The invention is described more closely below with reference to theappended drawings, where

FIG. 1 shows an end view of a block and illustrates schematically thecorrect and incorrect placing of triangular staves of wood during gluingtogether,

FIGS. 2A & 2B show sections through a first embodiment of a device forpressing together staves of wood during gluing, and also illustrate asuitable orientation of the annual rings of the staves of wood which areto be glued together,

FIG. 3 shows a section through a schematically illustrated secondembodiment of a device for pressing together staves of wood duringgluing,

FIG. 4A shows an end view through a schematically illustrated thirdembodiment of a device for pressing together staves of wood duringgluing,

FIG. 4B shows a schematic longitudinal section through a part of thedevice shown in FIG. 4A, and

FIG. 5 shows an embodiment with HF-heating of the glued block duringpressing.

FIGS. 6A and 6B shows a perspective view, partly in section, and alongitudinal section along the broken line VI—VI in FIG. 6A,respectively, of joints in the longitudinal direction.

DETAILED DESCRIPTION OF THE FIGURES

In FIG. 1 triangular staves of wood are shown laid out side by sidealternatively with the base facing downwards and alternatively with thebase facing upwards and are seen from one end. The outermost staves ofwood 1 and 2 are essentially right-angled between the base and the outerside. The other staves of wood 3-8 are preferably isosceles, or, evenbetter, equilateral. It is also possible within the scope of theinvention to conceive using irregular triangular cross-sections but itis not directly practical to use such. FIG. 1 shows that it is known inthe prior art during gluing to press against the outermost staves ofwood 1 and 2 via press blocks 1′ and 2′, respectively, i.e. from thelongitudinal edge sides. In this case it is apparent that the staves ofwood are displaced vertically in relation to each other in a somewhatuncontrolled manner, as is evident from the Figure. A conventional presswith side forces also gives powerful friction on the outermost stavestowards the upper and lower sides and with consequently diminishing gluepressure towards the middle of the glued block leading to bad gluejoints and the risk of worsened quality.

According to the invention the glue joints are achieved through thetriangular staves of wood being pressed together from the broad sides.In the embodiment shown in FIGS. 2A and 2B, a press head 9 and 10 isplaced on each of the broad sides in order to hold the staves of woodwell pressed together during the formation of the glue joints. Anadjustable dolly 11 and 12 is placed by each of the outermost staves ofwood in order to hold together the staves of wood in the lateraldirection. Especially in this embodiment it can also be suitable toprovide a certain pressure against the staves of wood from the dolliesso that the staves of wood are well held together in the lateraldirection during the whole press operation.

A variant is to pump with pressure during the pressing together phase.This evens out the pressure force between the joints.

The wood material with a triangular-shaped cross-section is preferablylaid into the press with the annual rings directed essentially in linewith each other so that the material/block receives a similarexpansion/contraction at different moisture levels and therefore gives amaterial which, relatively seen, warps less than if the annual ringswere laid out in another way. Preferably they should be directedessentially transverse to the width of the block, as is shown in FIG. 2Aand 2B. In this way the movements due to moisture takes placeessentially in the direction of thickness of the finished block and notalong its width, which is an important advantage if the block is used,for example, as a floor covering or the like. Furthermore, after thepressing is finished, a sawing device can saw the completed glued blockinto thin sheets through cutting essentially parallel with the broadsides of the block.

FIG. 2A shows essentially isosceles pieces of wood. FIG. 2B shows thatalso gluing together of pieces of wood with a triangular cross-sectionwith a right angle, e.g. the angles 45°/45°/90°, can function with themethod according to the invention. Such triangular pieces of wood can beproduced by the well-known sawing pattern called quarter-sawing. Dollies11 and 12 determine the width of the block in the lateral direction, andthe pressure from the press on the extended surfaces causes the inclinedsurfaces to glide towards each other so that the transverse surfaces arepressed towards each other, by means of which a good glue joint is alsoachieved there.

Preferably, the essentially triangular-shaped wood elements—in order togive a satisfactory glue joint—should be displaced so that a certainpart of the peak lies above the surface of the base of the surroundingtriangles in order to ensure that the glue joint extends all the way upto the finished surface without faults. Furthermore, in this case narrowstripes are formed in the surface, which enhance the appearance of thesurface. The risk that the point comes under the base surface is large,as is illustrated at the joint between the staves of wood 3, 4 and 5 inFIG. 1, when the pressure of the press in the glue joint diminishesdrastically and the glue joint becomes poor. Furthermore, in such a casethe block must be planed down in order to have an acceptable appearance.

FIG. 3 shows an embodiment in which the press heads 13 and 14 areprovided with parts 15 and 16, respectively, which have spaces 17 and18, respectively, between them which can accommodate projecting peakedges of the staves of wood.

The press plates of the press can alternatively be equipped with a flatsurface with longitudinal grooves where the peak edges from thetriangular-shaped material can fit in. It should, however, be observedthat it is not necessary that the triangular staves of wood havecompletely pointed edges in the part which is directed towards a blocksurface. During planing it is practical, most of all for the sake offeed devices, to plane down one point of the triangular profile. Thistype of planed staves of wood can perfectly well be used in accordancewith the invention.

In another alternative the press plates have a relatively thick coatingof a material which is yielding to counterpressure from a projectingpart, such as a pointed edge, from the essentially flat glue joint platebut which is essentially non-yielding in general (not shown). A suitablematerial is therefore rubber or elastic or rigid soft plastic where thepointed edges during pressing are introduced into the material. Thematerial should be relatively stiff in order to be essentially lessyielding to the broad sides of the triangular staves of wood than totheir pointed edges. The material should have a low friction to theintroduction of the pointed edges and preferably also in the transversedirection at the joint between the material and the wood elements.

The press has an adjustable compartment, comprising e.g. adjustable sidepieces 19 and 20, respectively, for the insertion of the triangularstaves of wood lying beside each other. In this case the side piecesshould be made in such a way that the compartment corresponds to theexpected width of the produced block with suitable tolerances.

As shown in the embodiment in FIG. 3 of a press, each plate in the upperpart of the press, “cover”, can be equipped with a vertical forceproducer, e.g. hydraulically, which presses together the material whichis provided with glue during the adaptation. By means of thetriangular-shaped material, a vertical force is obtained which gives aneven pressure on each piece of material (stave) independent of the widthof the block, which gives good glue joints over the whole surface.

In this embodiment of the press, the pressure heads 13 and 14 are placedbetween an upper part 21 and a lower part 22. Hydraulic tractioncylinders 23 and 25 are placed on both sides and one of them iscontrolled during the opening of the press and the other during thepressing operation. Despite only two being shown, there should be atleast four, i.e. two on each side of the pressure-loaded region. Thepressure cylinder 23 is pivotally fastened at both ends to the upperpart 21 and to the lower part 22. Beside and inside the pressurecylinder 23, a pull rod 24 is pivotally fastened in the same way.

The pressure head 14 can be, but does not have to be, comprised as apart of the lower part 22. FIG. 3 shows that the hydraulic cylinder 25is rotatably mounted on the lower part 22 and equipped with a hook 26for hooking onto a peg 27 on the upper part 21. In this way the upperpart 21 is openable at one end and rotatable around the pull rod 24 bybeing pulled by means of the hydraulic cylinder 23 for easy placement ofthe triangular staves of wood and regulation of the side pieces 19 and20.

Pressing together occurs by means of the hydraulic cylinder 25 when itis hooked fast in the upper part 21. The hydraulic cylinder 23 is inthis case inactive. Between the upper part 21 and the pressing plate 13there is a force-distributing arrangement in order to give a pressureload which is as uniform as possible on the block of triangular staves.Two pressing blocks 28 and 29 are arranged over the pressing plate,which each are anchored to the pressing plate via at least two links 30,31 and 32, 33, respectively, which are somewhat movable transversely andwhich run in the same direction as the direction of grain of thetriangular staves of wood. At their front and rear ends the pressingblocks 28 and 29 are pivotally fastened to a block 34, which ispivotally fastened to the upper part 34. Through this construction,pressure is transferred from the upper part 21 to the pressuredistributor along only one line, which runs parallelly with the block,and a nearly uniform pressure distribution is achieved during tensioningof the hydraulic cylinder 25 even if the upper part 21 is placed at anangle. It should be noticed that for the process according to theinvention, the important thing is precisely to achieve a uniformpressure on both sides of the block and that this can be achieved evenin other ways than that shown in FIG. 3.

The small amount which the point edges on the triangular staves of woodstick up over the surface of the glued-together block, forms a verysmall part of the total block volume and therefore gives the possibilityto produce a block with good-quality glue joints with a low volumetricloss. On the other hand, a fault of the type which is shown in FIG. 1with sunken point edges during planing down naturally gives an extremelylarge cost/volymetric loss for a comparable quality level.

In a third embodiment shown in FIG. 4A the pressure units are formed onthe base sides of the glued block by means of a number of loose and/orguidable flat plates on a foundation 37 and 38, respectively, upon whichthe pressure is applied in a way as described in connection to FIG. 3.The plates 39 and 40, respectively, placed on the foundation 37 and 38are movable in the transverse direction, e.g. along guides (not shown),in order to give a space between them for each point edge of thetriangular board and are controllably adjustable for the variousconceivable dimensions of the material. The adjustment of the plates 39and 40 can possibly take place by hand but also with the help ofelectronic control systems and performed during the unloaded conditionof the press, i.e. before the hydraulic cylinder 25 in the lockedposition is activated.

The side supports are normally controllably adapted to fit the desiredfinish dimension and chosen material dimension. By means of the pressureon both broad sides the staves of wood can be moved in the transversedirection to the desired dimension because the point edges during theapplied pressing action are able to stick out without thereby contactingany obstacle.

The block can also be manufactured in a continuously working press whichis a modification of that described in connection to FIG. 4A. This presscan have plates 39 and 40 with a significantly smaller length than thelength of the staves of wood in their direction of grain. The sidepieces 19 of the press can even be displaceable for movement in thelongitudinal direction along the block. When a section of the gluedblock is pressed and ready, the press is opened and the plates moved tothe next section.

Preferably the staves of wood of the block are placed stationary,possibly through their ends being firmly anchored (not shown). Themoving parts of the press can thereby during movement ran against e.g.ball races, which give low friction in the longitudinal direction andhigh stiffness in the pressure direction. The movable parts can then bereturned to their original position by means of, for example, a returntransport or hinged arms so that a flat, continuous (and, in thelongitudinal direction, easily movable) pressure is given to thematerial. There are different known solutions for performing this. Theseare normal for chipboard presses. Here the plates are equipped withlinks and go round runner wheels. Underlying supports are designed sothat the edges of the plates do not make impressions in the blocks. FIG.4B shows schematically such an embodiment in a longitudinal section ofpart of the upper part of the press, where the plates 39 are shaped aslinks and a ball race 45 is situated between the pressure plate 37 andthe plates 39. The pressure plate 37 is moved stepwise in the directionof arrow A along the stave of wood 46, while at the same time thejoined-together plates 39 step by step are moved downwards towards thestaves of wood by the pressure plate 37.

The pressure plates can instead be equipped with heating elements or beheated by means of IR-technique on the outside in order for the glue inthe glued block to set quickly and surely during the pressing operation.Preferably, a glue should be chosen which does not set quickly before ithas been subjected to heat, so that the gluing together does not takeplace outside the portion of the glued block which has been subjected topressure. A suitable glue in this connection is phenol/rescorcinol glueor melamine glue for weather-resistant products or PVAC-glue for indoorproducts.

In another alternative, microwave energy or HF-heating can be providedfor setting the glue. An embodiment of a press with these features isshown in FIG. 5. The staves of wood which are to form the glued block 50are placed on the base plate 51 between the side pieces 52 and 53. Anadjusting means 54 for these is indicated schematically. The upper part55 of the press in this embodiment is guided to press against the gluedblock 50 by hydraulic cylinders 58 and 59 arranged beside each other,and comprises a high-frequency heating part 56 supplied from ahigh-frequency source HF. The heating part is of known type andconsequently does not need to be described more closely. The plates 57facing towards the glued block can in this connection be provided withopenings, which in the main are greater than the wavelength of thesupplied energy, or the plates can be made of a non-conducting materialwith a suitably low ε, e.g. a suitable composite, which the suppliedenergy can pass through, whereby the setting can take place more quicklywith a higher productivity as a consequence. A suitable glue in thisembodiment is e.g. PVAC-glue.

In this alternative, the triangular staves of wood are laid after eachother in the press, either end to end with the adjacent staves of woodin the transverse direction displaced in relation to each other for thesake of strength, or with each end (and/or at least one of the longsides) of the staves of wood prepared for splicing (finger splices)which gives a higher total strength.

As apparent from FIGS. 6A and 6B, it is also possible to use theprinciples according to the invention for providing a glue fasteningbetween the staves of wood laid after each other. Each stave can beobliquely cut even at its ends before the stave is laid together withanother obliquely sawed stave at its end to make an extended stave. Theindividual staves in a block could be extended at different lengths asillustrated at the end cuts 61, 62 and 63. In this way, endless blockscould be created which could be cut in arbitrary lengths. The obliqueend cuts could be smooth as at 61 and 62 or spliced as at 63, where thefinger cut is visible from the surface of the block, or as at 64 showingan end cut having the slicing parallel to the surface of the block suchthat only a straight line is apparent from the block surface. Aparticular oblique cut of this kind is shown at 65 in FIG. 6B in thatthe cut is smooth at the ends and in the middle in order not toinfluence the surface parts and in order to make it possible to dividethe block into two and still having a nice surface at the cut. Thefinger cut could also be perpendicular to the block surface asillustrated at 66.

The kind of extension discussed above will save wood stuff, providevalid blocks since each stave will be supported by the adjacent stavesat the joints and make it easy to produce blocks of wished and arbitrarydimensions.

What is claimed is:
 1. Process for the manufacturing of only asingle-layered glued block of triangular cross-section, elongated staves(3-8) of wood where the staves for forming the block are laid besideeach other in only a single row lying in only a single plane withalternate staves (4) with their base sides downwards and alternate ones(3) with their base sides upwards and unset glue applied between alladjacent surfaces between the staves when placed in the single row,wherein a main pressure force to glue the staves firmly together isexerted transverse to the base sides of the staves (3-8), which isobtained by a movement of only a common pressure plate (10, 13, 37) onlyperpendicular to said single plane while the staves are locked betweentwo lateral stops.
 2. Process according to claim 1, characterized byproviding cavities in the pressure plate and/or a support plate in frontof the point edges of the triangular staves of wood or providing amaterial for the pressure plate flexible when actuated by the pointedges in order to provide pressure force with considerably higher forceonto the base sides of the triangular staves than on their opposite peakedges.
 3. Process according to claim 1, characterized in that sidesupports (11, 12; 19, 20) are positioned against the longitudinal edgesbefore the pressure force is exerted on the base sides.
 4. Processaccording to claim 3, characterized in that the side supports arerigidly set.
 5. Process according to claim 3, characterized in that theside supports are controllably adjusted.
 6. Process according to claim3, characterized in that a pressure force is also exerted on the sidesupports in a direction towards the glued block.
 7. Process according toclaim 1, characterized in that the glued block is heated up in thepressing region during pressing towards the base sides of the staves. 8.Process according to claim 7, characterized in that the heating takesplace through heating of said pressure plate.
 9. Process according toclaim 7, characterized in that the heating takes place throughmicrowave- or HF-heating of the pressure plate.
 10. Process according toclaim 1, characterized in that each said stave is obliquely cut at itsend and joined with another stave also cut obliquely at its end toprovide an extended stave, in that several staves are extended in thisway, and in that several extended staves are laid beside each other. 11.Process according to claim 1, characterized in that each said stave isobliquely or transverse cut using finger joint technique at its end andjoined with another stave also cut accordingly at its end to provide anextended stave, in that several staves are extended in this way, and inthat several extended staves are laid beside each other.
 12. Processaccording to claim 1, wherein said block has two major oppositesurfaces, and the annual rings of the wood are substantially transverseto said surfaces.
 13. Press arrangement for manufacturing of only asingle-layered glued block made of triangular cross-section staves ofwood, where the staves are laid beside each other in only a single rowlying in only a single plane with alternate staves with their base sidedownwards and alternate ones with their base sides upwards and glueapplied between adjacent surfaces between the staves, a pressure plate(10; 13, 15; 37, 39) is provided facing towards the upwardly facing basesides of the staves, and a supporting plate (9; 14, 16; 38, 40), forsupporting the downwardly facing base sides of the staves, side supportsplaced along each long side edge of the laid out staves to lock thestaves between lateral stops, and a pressure supplying device (21-25,28, 29, 34) moving only the pressure plate towards the bases of thetriangles of the staves only perpendicular to said single plane in thedirection towards the support plate during activation of the pressureplate; characterized in that the support plate and/or the pressure platehave cavities directly in front of the point edges of the triangularstaves of wood.
 14. Press device according to claim 13, characterized inthat the side supports (11, 12; 19, 20) are placed at a mutual distancewhich is adapted to the desired transverse dimension of the block. 15.Press device according to claim 13, characterized in that the supportplate and/or the pressure plate have a coating of a material which isyielding to pressing from a point edge of the staves which extend outbetween two adjacent base sides but which is otherwise essentiallynon-yielding.
 16. Press device according to claim 13, characterized by aheating arrangement for heating the staves during applied pressure. 17.Press device according to claim 16, characterized in that the heatingarrangement is a microwave- or HF-heating device.
 18. Press deviceaccording to claim 13, characterized in that the triangular staves ofwood are laid with the annual rings oriented essentially transverse tothe opposite block surfaces.
 19. Press device according to claim 13,characterized in that, when laid in the press device, some of said staveare obliquely cut at its end and joined with another stave also cutobliquely at its end to provide an extended stave, and the extendedstaves are laid beside each other, the pressure plate is provided acrossthe joints between the extended staves.
 20. Press arrangement formanufacturing of only a single-layered glued block made of triangularcross-section staves of wood, where the staves are laid beside eachother in only a single row lying in only a single plane with alternatestaves with their base side downwards and alternate ones with their basesides upwards and glue applied between adjacent surfaces between thestaves, a pressure plate (10; 13, 15; 37, 39) is provided facing towardsthe upwardly facing base sides of the staves, and a supporting plate (9;14, 16; 38, 40), for supporting the downwardly facing base sides of thestaves, side supports placed along each long side edge of the laid outstaves to lock the staves between lateral stops, and a pressuresupplying device (21-25, 28, 29, 34) moving only the pressure platetowards the bases of the triangles of the staves only perpendicular tosaid single plane in the direction towards the support plate duringactivation of the pressure plate; characterized in that the supportplate and/or the pressure plate comprise laterally adjustable platesections (40, 39).
 21. Press arrangement for manufacturing of only asingle-layered glued block made of triangular cross-section staves ofwood, where the staves are laid beside each other in only a single rowlying in only a single plane with alternate staves with their base sidedownwards and alternate ones with their base sides upwards and glueapplied between adjacent surfaces between the staves, a pressure plate(10; 13, 15; 37, 39) is provided facing towards the upwardly facing basesides of the staves, and a supporting plate (9; 14, 16; 38, 40), forsupporting the downwardly facing base sides of the staves, side supportsplaced along each long side edge of the laid out staves to lock thestaves between lateral stops, and a pressure supplying device (21-25,28, 29, 34) moving only the pressure plate towards the bases of thetriangles of the staves only perpendicular to said single plane in thedirection towards the support plate during activation of the pressureplate; characterized in that its press region extends over a part of thelength of the glued block and is movable in order to displace thepressure zone along the plate at suitable time intervals adapted to thesetting time of the glue used.